UNDERSTANDING CODE MOBILITY

The technologies, architectures, and methodologies traditionally used to develop distributed applications exhibit a variety of limitations a nd drawbacks when applied to large scale distributed settings (e.g., t he Internet). In particular, they fail in providing the desired degree of configurability, scalability, and customizability. To address thes e issues, researchers are investigating a variety of innovative approa ches. The most promising and intriguing ones are those based on the ab ility of moving code across the nodes of a network, exploiting the not ion of mobile code. As an emerging research field, code mobility is ge nerating a growing body of scientific literature and industrial develo pments. Nevertheless, the field is still characterized by the lack of a sound and comprehensive body of concepts and terms. As a consequence , it is rather difficult to understand, assess, and compare the existi ng approaches. In turn, this limits our ability to fully exploit them in practice, and to further promote the research work on mobile code. Indeed, a significant symptom of this situation is the lack of a commo nly accepted and sound definition of the term ''mobile code'' itself. This paper presents a conceptual framework for understanding code mobi lity. The framework is centered around a classification that introduce s three dimensions: technologies, design paradigms, and applications. The contribution of the paper is two-fold. First, it provides a set of terms and concepts to understand and compare the approaches based on the notion of mobile code. Second, it introduces criteria and guidelin es that support the developer in the identification of the classes of applications that can leverage off of mobile code, in the design of th ese applications, and, finally, in the selection of the most appropria te implementation technologies. The presentation of the classification is intertwined with a review of state-of-the-art in the field. Finall y, the use of the classification is exemplified in a case study.